Mammalian glycoprotein oligosaccharides are commonly built from a limited number of monosaccharides. Nevertheless, structural diversity is vast, mainly due to complex branching patterns. Glycosylation sites on glycoproteins commonly display microheterogeneity in that they can be fully or partially occupied by structurally diverse oligosaccharides. Consequently, a glycoprotein is not typically isolated as a single structural entity, but rather as a set of glycosylation variants known as glycoforms.
There is evidence that both the in vivo and in vitro properties of glycoproteins are affected by changes in occupancy and/or the precise oligosaccharide attached to a particular site. Distinct biological properties have been correlated with the presence of particular glycoforms.
A method for determining the composition and sequence of polysaccharides in a carbohydrate-containing molecule (“glycomolecule”) has been described (see, e.g., WO00/668688, WO01/84147, WO02/37106, and WO02/44714). In this method, termed UC-FINGERPRINT™ analysis (also known as GMID™ analysis), a carbohydrate-containing molecule is added to a substrate containing an array of saccharide-binding agents (typically antibodies or lectins). Saccharide-binding agents bound to the glycomolecule are identified, and the binding information is used to obtain composition and sequence information of the monosaccharide subunits in the polysaccharide.